Amazon CEO Jeff Bezos REUTERS/Rick Wilking Amazon is hardly the same company it was in 1999, when e-commerce was still a relatively small industry and the budding online retailer exclusively sold books.

Today, the world's fourth-most valuable company ships a mind-boggling number of goods to billions of people around the world.

By some accounts, it has essentially created America's largest company town in Seattle. Recently, Amazon announced plans to spend $5 billion on a second headquarters, for 50,000 employees, somewhere in North America.

There are a number of ways to look at Amazon's size, and each is just as unfathomable as the last.

1/

7.5% of Seattle's working-age population are Amazon employees.

Jason Redmond/Reuters

Amazon has more than 300,000 employees worldwide, and 40,000 in Seattle alone.

As a portion of the city's working-age population — roughly 528,000— that comes out to 7.5% of the city working at Amazon.

For perspective, if the same portion of New York City's adults worked for one company, that company would have about 488,000 locals on staff.

2/

Amazon accounts for 43% of all online sales.

Caroline Cakebread/Business Insider

Amazon used to be a way to buy books online; today, it's the default buying site for just about everything, especially for people who have Amazon Prime.

An analysis by Slice Intelligence released in February found that 43% of all US online retail sales were done through Amazon in 2016.

That's up from 33% in 2015 and 25% in 2012.

3/

1 out of every 4 US adults has Amazon Prime.

Amazon

Speaking of Amazon Prime, the company now counts approximately 63 million people among its subscriber base, or about 25% of the total US adult population.

That number may underestimate the true coverage, however, since it doesn't account for multiple adults in one household all sharing the same Prime account.

4/

Amazon ships 1.6 million packages a day.

Matt Cardy / Stringer / Getty Images

Amazon fulfillment is a beast of its own.

A report from 2013 (the latest year for which data are available) found Amazon shipped 608 million packages that year, or 1.6 million packages a day.

As of 2015, Amazon estimated its fulfillment centers were within 20 miles of 31% of the US population, and within 20 miles of 50-65% of its core, same-day-accessible market.